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Serotonin, impulsivity, and eating disorders

Posted Aug 23 2008 10:35pm
Serotonin is the brain chemical we've all come to know and love. It's sometimes called the "happy chemical." Why? People with depression tend to have low levels of serotonin in the brain. So do people with anxiety disorders. And bulimia nervosa .

Anorexia appears to be a little different. While researchers know that people with anorexia have abnormal serotonin levels both during illness and after recovery, the levels in recovered anorexics tend to be higher than usual. A review article from 1997, followed by a study from 1998 , says that

Certain traits, such as negative affect, behavioral inhibition, compliance, high harm avoidance, and an obsessive concern with symmetry, exactness, and perfectionism, persist after recovery from anorexia nervosa . These persistent symptoms raise the possibility that such traits exist premorbidly and contribute to the pathogenesis of this disorder. Such traits could be associated with increased brain serotonin activity.

But an interesting study came out recently that linked low serotonin levels to impulsivity and aggression.

A press release said that the study results

"highlight why some of us may become combative or aggressive when we haven't eaten. The essential amino acid necessary for the body to create serotonin can only be obtained through diet. Therefore, our serotonin levels naturally decline when we don't eat, an effect the researchers took advantage of in their experimental technique.

The research also provides insight into clinical disorders characterised by low serotonin levels, such as depression and obsessive compulsive disorder ( OCD ), and may help explain some of the social difficulties associated with these disorders."

Restrictive eating causes a drop in serotonin, temporarily normalizing mood. Then, of course, the not eating continues and serotonin continues to drop. This drop in serotonin also helps to (temporarily) decrease anxiety.

The chaotic eating surrounding bulimia may also help explain the dramatic rise in impulsivity seen in people with this illness. Besides possibly having a lower-than-average level of serotonin, the periods of food restriction that often accompany bingeing and purging could further lower serotonin levels, making the impulses to binge and purge even harder to resist. Purging also lowers serotonin, compounding the situation even further.

It also, I might add, explain why dieters are so darn cranky!

If anyone can help explain why people with anorexia have higher rates of pre -illness OCD and high serotonin levels (when OCD is associated with low serotonin), I would greatly appreciate it.
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